Disclaimer : Whenever there is propane there is risk. If you decide to refill your propane tanks yourself, you have to understand that you do it at your own risk. These cylinders aren't DOT approved for refilling. This means that you can't take your cylinders to the local propane-equipped service station and have them refilled. That's against the law. And refilled cylinders can't be sold commercially. And commercial operators can't transport refilled cylinders across state lines. There are all sorts of limitations and potential liabilities associated with refilling these cylinders. It's perfectly legal to refill them for personal use, however.
There is some safety precautions that you have to take when refilling your disposable propane cylinders and you will need to handle it properly and observe all the best-practice safety protocols.
#1 Always do the refill process outside.
#2 Never smoke during the entire process.
#3 Be sure there is no open flame in the area.
#4 Wear safety glasses and protection gloves for added safety.
Again, I am not responsible for any accident that can happen when you refill your own disposable propane tank.